(1) Technical Field
This invention relates to submersible deep well pumps of the type employed to pump oil from wells.
(2) Description of the Prior Art
Prior art devices of this type have used a variety of different designs to displace liquid by piston pumps and check valves. See for example U.S. Pat. Nos. 356,750, 445,962, 814,312 and applicant's own U.S. Pat. No. 4,137,017.
In U.S. Pat No. 445,962, a pump is disclosed having a three-chamber configuration with a pump rod and float valve.
U.S. Pat. No. 356,750 discloses a pump with a piston tube that displaces fluid through check valves to the surface.
In U.S. Pat. No. 814,312, a pump is shown having a pump plunger rod moving within a cylinder with a pair of check valves regulating the flow of fluid within the chamber and up the pump plunger rod.
Applicant's U.S. Pat. No. 4,137,017 discloses a deep well submersible pump having a hollow piston rod which displaces oil through a check valve and up the hollow piston rod itself.
Applicant's present invention utilizes an apertured hollow piston rod with a secondary piston secured thereon and a series of vents, which in combination provide a hydraulic spring action to limit the travel of the hollow piston rod by utilizing the pressure within the well, the weight of the string and an outside pressure source to move the oil to the surface.